Length adjusting devices (LADs) are often referred to by a variety of names by arborists, linesmen, climbers, and other workers or athletes engaged in aerial pursuits. Other such terms include rope grabs, rope adjusters, rope clamps, ascenders, descenders, descent control devices, microscenders, micrograb rescuescenders, etc. These devices typically consist of a frame supporting an axle around which an engaging cam may pivot. The cam has engaging teeth on a portion of its outer perimeter. Rotation of the cam moves these engaging teeth between: a position at which a rope or webbing may readily slide between an inner portion of the frame and the engaging teeth; and a position where the engaging teeth prevent passage of the rope or webbing through the frame. An eye or other connection point is fixed on an outer arm of the cam assembly. The eye allows attachment of a device (e.g., a work positioning lanyard, carabiner, or the such) to a body belt D-ring or attachment device to the length adjusting device.
For simplicity, the term length adjusting device as used herein is intended to include any length-adjusting device that utilizes a cam that bears rope or webbing engaging teeth, such devices intended to selectively allow and disallow passage of rope or webbing through the device.
Referring to FIGS. 1a and 1b, there are shown an exploded view and an assembled view, respectively, of a rope grab of the prior art, generally at reference number 100. Rope grab 100 is a length adjusting device (LAD) Model 5004B known as a “Buckgrab” manufactured by Buckingham Manufacturing Co., Inc. of Binghamton, N.Y. Rope grab 100 has a body 102 and axle 104, a cam assembly 106 having a proximal cam end 108 with engaging teeth 110 and having a hole 112 therethrough. A nut 114 is used to secure axle 104 bearing cam 106 within body 102. A cable 116 is used to secure cam 106 to body 102 when rope grab 100 is disassembled to insert a rope or webbing 118.
As may readily be seen, cam 106 has an eye 120 disposed at a distal end 122 of cam assembly 106. The eyehole 124 has an axis 126 that is substantially perpendicular to the plane of the paper on which FIG. 1b appears and perpendicular to the major axis 128 of cam assembly 106.
The distal cam end 122 serves as a release to allow passage of rope or webbing 118 by causing rotation of cam assembly 106 around axle 104. The rotation of cam 106 about axle 104 selectively engages and disengages the engaging teeth 110 against rope or webbing 118, thereby to selectively allow and disallow passage of rope or webbing through body 102.
The orientation of cam eyehole 124 (FIGS. 1a and 1b) is problematic as discussed in detail hereinbelow.